urban planning

Sea Levels Might Be Rising Much Faster Than Expected. What Should New York Do to Avoid Being Swamped?

The Dryline Photo: Bjarke Ingals Group

When climate scientist James Hansen informed the world this week that the seas could rise much faster than conventional wisdom conceived, his predictions conjured apocalyptic images of submerged coastal cities and waters lapping at the Brooklyn Heights Promenade. The current international target of containing global warming to a two-degree (Celsius) rise in average atmospheric temperature would be “highly dangerous,” he and 16 colleagues warn in a paper that was controversial even before its publication. Even modest warming might cause sea levels to rise ten feet in coming decades, three times the accepted maximum. It could trigger higher tides, tougher storms, and longer droughts than anyone anticipated. Vulnerable cities could get wiped away. In New York, the floodplain would spread, putting hundreds of thousands of people in the way of potentially deadly waves. New buildings constructed to an obsolete code and raised above levels once considered safe might find themselves threatened after all.

It will take some time for scientists to assess that volley of pessimism, but in the meantime it’s good to know that at least the New York region is actually doing something to prepare for a watery future. The question is, if Hansen is right, is it doing enough? Jolted by the experience of Hurricane Sandy in 2012, when 14-foot waves washed over the FDR Drive and turned Red Hook and Chelsea into wetlands, the U.S. Department of Housing and Urban Development came up with $1 billion, to be spread among half a dozen winners of a competition called Rebuild by Design, cultivating ideas to protect the metropolitan area. Among them is the “Dryline,” a system of meadow-covered hills, absorbent parks, and temporary watertight barriers that would drop below the elevated portions of the FDR Drive, protecting lower Manhattan. But like all six winners, the Dryline, designed by a multidisciplinary team led by the Bjarke Ingels Group (BIG), bases its plans on the recommendations of the International Panel on Climate Change, which foresees a maximum three-foot rise in sea levels by 2100, a much more modest and gradual change than Hansen’s team envisions. If the paper’s new omg! warnings prove persuasive, will all the architects, planners, and engineers who have spent two years working on the problem have to scrap everything they’ve done and start trying to ward off imminent total calamity?

Not at all, says Judith Rodin, president of the Rockefeller Foundation (which partially funded Rebuild by Design) and the author of The Resilience Dividend. “Science is going to continue to give us more information all the time, so resilient design bakes in the presumption that the knowledge is going to continue to grow.”

Photo: Bjarke Ingals Group

Predicting the local effects of global climate change is a game of probability. Storms might become more frequent and throw higher waves at the city’s edge, but whether your basement will be flooded or your store shuttered by a particular storm will depend on the moon, the season, and a thousand other unknowable variables. The best that we can do is prepare for contingencies and plan to bounce back after one of nature’s assaults rather than try to lock them out completely. Hansen’s report doesn’t change that flexible approach — rather, it affirms its importance.

None of the [Rebuild by Design] projects seeks to eliminate flooding 100 percent,” Rodin points out. The guiding philosophy of resilience is: “Do everything you can to manage that which is avoidable and to avoid that which is unmanageable.”

Henk Ovink, the Dutch climate-change guru who ran the competition, says that planning for climate change requires a sweeping societal transformation — in personal habits, in the way cities are planned, in the resources we extract, transport, and exploit, in the politics of energy. The paradox is that it also demands a combination of urgency and patience. “We have no time to waste, but we also have to think in terms of generations to come. Cultural change never comes overnight.”

In the Netherlands, Ovink says, “We’ve been working with water for thousands of years. We’ve constantly had to reinvent, and whatever we do, nature is flexible. There is no silver bullet.” The key is to make plans adaptable. Try to seal off New York Harbor with a big, expensive floodgate, and you’re locked into dealing with potentially wrong predictions. But a complex network of local measures — a berm here, an inflatable tunnel plug or deployable barrier there, a necklace of spongy parks — can be tweaked along the way, rebuilt down the line, and combined with other solutions. You can’t avoid uncertainty; you can only plan for it.

Is NYC Doing Enough to Prepare for Rising Seas?